On July 3, the morning after a bomb had destroyed the U.S. Senate’s reception room, a German sympathizer named Erich Muenter shot J. P. Morgan, Jr., in his Long Island mansion for having represented the British government in the negotiation of war contracts in America. Muenter had taught German at Cornell and Harvard before disappearing after being indicted for poisoning his wife in 1906.

Muenter later claimed that he only wanted to scare Morgan into using “his influence to prevent the exportation of arms and ammunition” to Great Britain, but this defense had little credibility alongside Muenter’s boasts that he had also planted the Senate bomb. His escape from Washington proved to be much easier than one from a millionaire’s mansion. Wounded twice in the groin, Morgan still managed to wrestle Muenter to the floor, where a butler knocked the gunman senseless with a chunk of coal. “It was a most disagreeable experience,” said the burly banker afterward, “though it is not as painful as I imagined it would be to be shot. …” Muenter committed suicide in prison two weeks after the shooting; his activity increased fears that the United States was swarming with German agents.

The German conspiracy theory was reinforced later in the month when Dr. Heinrich F. Albert, the head of German propaganda in the United States, left his briefcase in a New York City elevated-train car on July 24. A U.S. Secret Service agent named Frank Burke, who had been tailing Albert, grabbed the case and, seeing Albert coming back for it, fled the station. Burke caught a streetcar and escaped from Albert’s frantic pursuit only by persuading the conductor to outrun the madman who was chasing him and cursing in breathless German. Documents in the briefcase, most written in German and marked Streng Vertraulich (“strictly private”), detailed an extensive network of espionage and subversion throughout the United States.

Because the United States was not at war with Germany, the Wilson administration had had no legal right to take the briefcase, but it decided to release the documents to the press anyway. “It may, in my opinion, even lead us into war,” wrote the presidential adviser Colonel House to Wilson, “but I think the publication should go ahead. … it will make it nearly impossible [for Germany] to continue the propaganda.”

Details from documents released to the New York World in August undermined an American neutrality that was already in doubt after Germany’s sinking of the ocean liner Lusitania in May. “Albert’s portfolio was a veritable box of Pandora,” wrote George Sylvester Viereck, the editor of the GermanAmerican newspaper The Fatherland . “It unloosed every half-hatched plan of the Germans; the inner workings of the propaganda machine were laid bare. … The loss of that portfolio was like the loss of the Marne.”